Inside Aircraft Black Box Recorders

When a plane goes down, one of the first things safety investigators do is search for its black box recorder, which can provide a valuable starting point for determining what went wrong. It’s an essential tool, and it’s come a long way from the boxy recorders of the 1950s.

First off, the black box isn’t black – it’s painted bright orange so that it’s easier to locate at a crash site. And in most cases it’s actually two boxes: one for voice communication and the other for data. The cockpit voice recorder (CVR) is fairly straightforward – it collects sounds from the microphones, earphones and an area recorders mounted on the roof of a cockpit, storing two hours of audio with a sturdy digital recorder that’s less susceptible to moisture and heat than the magnetic tape recorders of yesteryear (before that, wire recorders were used). CVRs are battery powered so that they’ll operate even if a plane’s electrical system is shot.

A flight data recorder (FDR) performs the same function, except that it measures data on various aspects of a plane’s performance. A device called a flight data acquisition unit gathers and preprocesses information about 88 different performance parameters and sends snapshots of that data to the FDR for storage. Updated info is collected every few seconds, though that frequency bumps up if a plane seems to be in trouble.

A broken or lost recorder is useless, which is why modern models are built to last. International standards require that voice and data recorders are able to withstand high-temperature fires, salt water immersion, deep sea pressure, and impact velocity of 270 knots. CVRs and FDRs are covered with thick insulation and a steel or titanium shell, and many are designed to self-eject from a plane at the moment of impact. Others are equipped with emergency location devices, and they’re always located in an aircraft’s tail section, where they’re less likely to be crushed by the direct impact of a crash.

Data recorders are most often associated with tragedy, but they don’t have to be. Today, the same information studied by investigators to determine the cause of a crash is sometimes used to measure such things like fuel efficiency and crew behavior.

Speaking of crew behavior, pilots have aggressively opposed moves by the the National Transportation Safety Board to take things up a notch by installing comprehensive image recorders that would show cockpit conditions. They say it constitutes a Big Brother-style privacy violation.

It may be that cockpit recorders disappear altogether in the future.
Technology that transmits an aircraft’s voice and data to hardware on the ground is already being used by NASA, and may become more common moving forward.